boot_kstrtoul(9)

✨ boot_kstrtoul(9) ✨

okay so bestie, welcome to the Kernel API Manual 💖 this one is short and sweet and it's literally just "string goes in, unsigned long comes out" — let's get into it 🎀

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🌸 NAME 🌸

boot_kstrtoul — convert a string to an unsigned long 💅

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🦋 SYNOPSIS 🦋

int boot_kstrtoul (const char *s , unsigned int base , unsigned long *res );

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🎀 ARGUMENTS 🎀

• s — the start of the string, bestie. it must be null-terminated, and it may also include a single newline before its terminating null (yes, one, don't get greedy 🙈). the first character may also be a plus sign, but not a minus sign — no negatives allowed, periodt.
• base — the number base to use. the maximum supported base is 16 (that's the ceiling, we don't go higher ✋). if base is given as 0, then the base of the string is auto-detected with the conventional semantics: if it begins with 0x the number will be parsed as a hexadecimal (case insensitive, so 0x and 0X both slay), if it otherwise begins with 0 it will be parsed as an octal number, and otherwise it will be parsed as a decimal. it's giving detective energy 🔍
• res — where to write the result of the conversion on success. that's the drop-off point 📦

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💜 DESCRIPTION 💜

okay so here's the tea ☕ this returns 0 on success, -ERANGE on overflow (number too big, it literally can't even 😭), and -EINVAL on a parsing error (the string said something unparseable and we're not entertaining it 💀).

it's used as a replacement for the simple simple_strtoull. lowkey iconic of it to step in like that 👑

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🌈 SEE ALSO 🌈

• Kernel file ./arch/x86/boot/string.c
• simple_strtoull(9)
• strlen(9)
• strstr(9)
• strchr(9)

go read those too, iykyk 🫶

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ngl bestie, remember: no minus sign, max base 16, and always check that return value or you WILL be sad 🙈

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and that's the whole page, fr fr 💖✨ this one lives in ./arch/x86/boot, dated October 2026 — mwah, catch you in the next manpage, bestie 🎀🦋💜